Patent GB-831936-A (GB)
Title: Vacuum filling and weighing machine
Inventor: KNOBEL MAX
IPC: B65B31/02
Filed: 1958-06-26
Abstract: 831,936. Packaging machines. PNEUMATIC SCALE CORPORATION Ltd. June 26, 1958, No. 20561/58. Class 94(1). [Also in Groups XVIII and XXIX] In a vacuum filling and weighing machine, the vacuum filling head 20 and weighing apparatus 10 are enclosed in an airtight chamber 16 and the weighing apparatus is associated with control means 30 responsive to a predetermined weight on the platform 14 of the weighing apparatus for stopping the vacuum filling operation and opening the chamber 16 to atmosphere.. As shown the weighing apparatus is supported in a housing 17 below a platen 19 with its platform 14 registering with an opening 18 in the platen and in alignment with the filling head 20. The filling head is carried by a hopper 22 containing the filling material and has an inflatable rubber annulus 140 around its mouth to act as a feed cut-off when inflated. A longitudinal passage 36 in the wall of the head 20 connects a screened annular suction opening 34 at the head mouth with a suction pipe 38. A shroud 24 surrounds the head 20 and is movable axially thereof between a raised position, Fig. 3, allowing for replacement of the container 15 to be filled on the weighing platform 14, and a lowered position, Fig. 7, where it seals with a collar 26 on the head 20 and with the platen 19 around the opening 18. In its lowered position it defines with the housing 17 the airtight chamber 16. Movement of the shroud is effected by a double-acting pneumatic motor 28 controlled by a valve unit 58 which is manually operable to effect closing of the shroud at the start of a filling and weighing operation and mechanically coupled to the piston rod 114 of a valve 40 controlling the connection of the suction pipe 38 either to the vacuum source 44 or, when in the raised position of its piston 274, via a slide valve passage 122 and a vent 124, to atmosphere. Operation of the valve 40 to raise its piston 274 is by pressure air from a main 74 through a valve member 248, which is associated with the weight responsive means 30. The weighing apparatus, Fig. 7, comprises a vertical rigid platform support beam 12 connected in cantilever fashion to a rigid member 143 on the housing wall by upper and lower pairs of leaf springs 137, 139 of equal length. A coil spring 153 is connected between brackets 162 and 159 of the beam 12 and member 143 respectively, the bracket 162 having a spring attachment rod 161 which depends into attachment with a piston of a dashpot 164. Fine adjustment of the apparatus is provided by a coil spring 174 connected between a bracket 176 of the beam 12 and a stud 180 adjustably screwed into the lower housing wall 166, the stud being operable through bevel gears 182, 184 by a knob 186 outside the housing. To sense the deflection of the beam 12 on a predetermined weight of material fed into the container 15, an obturating member 212 is carried by the beam bracket 176 to co-operate with a nozzle 208 of the responsive means 30. The weight responsive means 30, Fig. 6, comprises a block 194 having two chambers 202, 242 which each communicate via a restricted throat and a passageway 196 with the air pressure main 74. The chamber 202 communicates also with a jet orifice 210 of the nozzle 208 which is aligned with the obturator 212 so that on deflection of the weigh beam 12 to move the obturator towards the orifice 210 the pressure within the chamber 202 acts through a passageway 214 on an expansible bellows 216 housed in a member 220 attached to the block 194, the bellows being expansible against a spring 232 and carrying a depending rod 228 on the end of which is an obturator 236 normally closing the orifice of a nozzle 240 communicating with the chamber 242. In operation, with a container 15 placed on the weighing platform 14, the lever 92 of the valve unit 58 is manually depressed. This rotates a pair of discs 78, 80 which are disposed in the sections 64, 70 of the valve associated respectively with the upper and lower air connections 60, 66, of the cylinder 52 of the motor 28, to connect the lower connection 66 with atmosphere and to connect the air main 74 with the upper connection 60. The piston 50 of the motor 28 is thus moved downwardly to lower the shroud 24. Depression of the lever 92 acting through an over-centre spring latched linkage 94, 96, 98 moves the piston rod 114 of the valve 40 downwardly to connect the suction opening 34 of the filling head with the vacuum source 44. As the shroud 24 closes the chamber 16, a pin 152 on the bracket 46 carrying the shroud operates a lever arm 150, Fig. 5, to raise a piston 142 of a valve 128 and thereby connect the annular rubber feed cut off with atmosphere to deflate same and permit flow of material through the head 20. When the desired weight of material fills the container, the deflection of the weigh beam 12 causes the obturator 212 to approach the nozzle 208 and the resultant rise in pressure in the chamber 202 effects expansion of the bellows 216 to move the obturator 236 away from the nozzle 240. This causes a drop in pressure in the chamber 242 which is communicated, via a conduit 254 with the cylinder 246 of the valve member 248. The valve piston 256 is thereby allowed to drop under the action of its spring 257 and the valve member 272 is thereby lowered to connect the air main 74 with the cylinder 270 of the valve 40. The piston rod 114 of the valve 40 is thereby raised to move the slide valve member 120 into a position sealing the vacuum source and venting the suction feed chamber 34 to atmosphere. At the same time the rod 114 rotates the rotary valve discs 78, 80 of the valve 58 to reverse the operation of the motor 28 and raise the shroud. Immediately the shroud moves, a pin 150 on the shroud bracket 46 lowers the piston 142 of the valve 128 to effect inflation of the feed cut-off annulus 140. The filled container is then replaced by an empty one and the operation repeated. In a modified arrangement, Figs. 14, 15, 16, the valve 128 controlling the feed cut-off is replaced by a pair of valves 300, 302, to effect partial cut-off, giving a dribble feed, as the weigh beam nears full deflection. The valves 300, 302 are identical but are operable at different air pressures determined by loading springs 358 of different tensions. The valve 300 is connected with a chamber 316, in the weight responsive means 301, which communicates with the nozzle orifice 210 so that when the pressure rises therein as the obturator 212 nears the orifice, the piston 306 of valve 300 is depressed against the loading of its spring 358 and allows air from the main 74, at a pressure determined by a regulator 324 to partially inflate the cut off annular 140. On full deflection of the weigh beam with consequential full obturation of the orifice 210 the pressure in the chamber 244 of the means 301 momentarily rises sufficiently to operate the valve 302 and permit full inflation of the cut off 140 before the nozzle 238 is opened by movement of the bellows to lower the pressure in the chamber 244 and trigger the valve 248. Resetting of the valves 300, 302 is effected by a solenoid 372 which is actuated by a micro-switch 382 operated by a cam 374 on the shroud bracket 46 towards the end of the movement of the shroud to its lowered position.